Mr Fini and his followers defected from the government in July, depriving Mr Berlusconi of a guaranteed parliamentary majority, and tensions between the former allies has plunged Italy into political paralysis.

The defeat came as a weekly magazine published alleged secretly filmed video footage of showgirls being driven to Mr Berlusconi's mansion, Villa San Martino, on the outskirts of Milan, without apparently undergoing any security checks by the police who protect the property.

Two of the women were named by Oggi ('Today') magazine as Flo Marincea, a 26-year-old television starlet on a programme called The Hottie and the Geek, and Lisandra Silva, a 23-year-old Cuban model.

They were filmed apparently entering an office in central Milan belonging to Lele Mora, a friend of Mr Berlusconi's and well-known celebrity agent who is being investigated for allegedly aiding and abetting prostitution.

The women, in high heels, minidresses and sunglasses, were apparently driven in a black Mercedes with tinted windows straight to the billionaire prime minister's villa on two occasions this summer – July 4 and 12.

The release of the video comes a week after Mr Berlusconi, 74, was summoned to appear in front of a parliamentary security committee amid concern from Italy's secret service that his alleged dalliances could endanger national security.

Massimo D'Alema, the committee's president and a former centre-Left prime minister, wrote to the prime minister again yesterday [Wed] to demand that he testify before the committee.

Luigi de Magistris, an MEP from the opposition Italy of Values party, said it was alarming that actresses and glamour models were granted such easy access to the premier's private residences.

"It is clear that this renders Berlusconi potentially vulnerable to blackmail and that puts at risk the security of the country," he said.

Mr Fini, the speaker of parliament and the co-founder of Mr Berlusconi's People of Freedom party, on Sunday called for the billionaire media mogul to resign and has voiced disquiet over the latest scandals to engulf the media mogul, involving a prostitute and a teenage belly dancer.

The feud between the two former allies is the factor most likely to bring down the government before its mandate expires in 2013, with many observers predicting a collapse within weeks.